The present invention relates to an excavation bit which is used to bore rock or earth surfaces.
The prior art drilling apparatus use an excavation bit for conventional (near surface to far surface) drilling, or a reverse reaming bit for far surface to near surface drilling, comprising one or more ground engaging formations mounted on the excavation bit. The ground engaging formations can be either drag, button, tooth, disc, point attack or other cutters on the bit to excavate rock. The main disadvantages with these types of bits is that to produce a larger hole will require more cutters, and as such a greater torque and thrust must be applied to the bit. Thus an operator is limited in the size of bores that can be excavated by the amount of power available from the driving equipment. The operation of conventional bits is performed by the revolving of the body of the bit, which then causes the cutters and carrier to rotate because the cutters are in contact with the earth surface. This action then allows the cutters on the bit to excavate the earth beneath the bit. The crushing and/or cutting thrust onto the surface being excavated must be totally supplied to the drill bit from a rotational unit which also produces thrust. Additional thrust is supplied by the weight of the bit which is an advantage in some excavations and a disadvantage in others.
The invention provides an excavation bit including a main body having a longitudinal axis which is coaxial with a longitudinal axis of a drill rod when connected to said bit, and first and second transverse axes, said axes being substantially orthogonal to each other; a carrier rotatably connected to said main body and having excavation means positioned about its periphery, said carrier having its axis of rotation generally in the direction of said first transverse axis and offset along said second transverse axis from said longitudinal axis of said main body, the axis of rotation of said carrier also being angularly offset from said first transverse axis, said excavation means having their centre of rotation offset along said axis of rotation from said longitudinal axis and or said second transverse axis; a reaction member mounted to the main body to engage the wall of a bore formed by said excavation bit; bearing means and seal means between said carrier and said main body; driving means to directly rotate said carrier about its axis of rotation, said rotation of said carrier producing rotation of said bit about said longitudinal axis.
The invention provides an excavation bit including a main body having a longitudinal axis and first and second transverse axes, said axes being substantially orthogonal to each other; at least two carriers rotatably connected to the main body having excavation means positioned about their respective peripheries, said carriers having their axes of rotation offset along said second transverse axis in opposite directions from said longitudinal axis, said axes of rotation generally extending away from said main body so as to position said carriers on opposite sides of said main body, said carrier further including each axis of rotation of receptive carriers is angularly offset from said first transverse axis, said excavation means having their respective centres of rotation offset along said axis of rotation from said longitudinal axis and or said second transverse axis; bearing means and seal means between said carriers and said body; driving means to directly contra-rotate said carriers, said rotation of said carriers producing rotation of said bit about said longitudinal axes when said excavation means engage earth to be excavated.
Preferably each axis of rotation remains in a plane through both the first transverse axis and the axis of rotation, which is substantially parallel to a plane containing the first transverse axis and the longitudinal axis.
Preferably when each carrier is viewed from the direction of the second transverse axis, the axes of rotation each lie at an angle to the longitudinal axis and the carriers angle towards each other.
Preferably the carrier or carriers are of an annular construction.
Preferably driving means includes a drive shaft which engages either directly or via an intermediate gear a gear on each carrier, to thereby rotate the carrier.
Preferably the carrier or carriers are driven by means of a single motor to drive one or two carriers or two motors to drive two carriers with the motor or motors being mounted within the main body.
Preferably the angle between the axes of rotation is in the range of less than but not equal to 180xc2x0 and greater than but not equal to 0xc2x0, such that a level of thrust in an excavation direction and a magnitude of force to cause rotation of the bit around the longitudinal axis, which will be appropriate for a type of material to be excavated.
Preferably the axis of rotation of each carrier is at an angle of between greater than but not equal to 0xc2x0 and less than but not equal to 90xc2x0 to the longitudinal axis, so as to produce a level of thrust in an excavation direction and a magnitude of force to cause rotation of the bit around the longitudinal axis, which will be appropriate for a type of material to be excavated.
Preferably the carrier or carriers approach but never cross the longitudinal axis.
Preferably the excavation means includes one of the following: pick; drag; roller button; roller tooth; disc roller cutter; blade; knife.
Preferably each carrier has as many excavation means mounted thereon to ensure that at any one time at least one excavation means of each carrier is in engagement with earth to be excavated.
Preferably the bit also includes a pilot bit rotatably mounted thereon.
Preferably excavating means are located on surfaces of each carrier adjacent or next adjacent the maximum perpendicular distance from the axis of rotation.
Preferably the excavation bit is constructed as a reamer and is adapted to be pulled through earth as excavation occurs.
Preferably affixed or rotatably attached to the main body is a stabiliser to assist the excavation bit keeping to a desired path.
Preferably the reaction member is a roller means to engage a bore surface.
Preferably the excavation bit also includes means to assist in the removal of debris from the bore or to lubricate the excavation bit in the bore.
Preferably the axis of rotation of the carrier, when there is only one carrier, is angularly offset from the first transverse axis, so that when the carrier is viewed from the direction of the second transverse axis, the axis of rotation each lies at an angle to the longitudinal axis.